Presence of Foam Cells in Kidney Interstitium Is Associated with Progression of Renal Injury in Patients with Glomerular Diseases

<i>Background:</i> Renal interstitial foam cells (FCs) are occasionally observed in various renal diseases. The goal of the present study was to determine the relationship between the formation of renal interstitial FCs and the degree of proteinuria and hyperlipidemia, as well as the progression of these diseases. <i>Methods:</i> 125 patients with Alport syndrome (AS), 192 patients with idiopathic membranous nephropathy (IMN), 388 patients with IgA nephropathy (IgAN), and 137 patients with focal segmental glomerulosclerosis (FSGS) were investigated retrospectively. <i>Results:</i> FCs were observed in various glomerular diseases. The frequency of interstitial FCs was 64.8% in AS, 21.4% in MN, 12.4% in IgAN, and 36.5% in FSGS. Regardless of the pathologic diagnosis of the glomerular disease, segmental glomerular sclerosis occurred more frequently in patients with FCs than in patients without FCs. In the AS or IgAN group, interstitial fibrosis was more severe, and levels of proteinuria and serum lipids were significantly higher in FC-positive patients than in patients without FCs. <i>Conclusion:</i> FC formation in renal interstitium is associated with the degree of proteinuria and hyperlipidemia in patients with AS and IgAN. The presence of FCs in renal interstitium may contribute to the progression of glomerular diseases.